<div class="refentry" title="glShadeModel"><a id="glShadeModel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glShadeModel — select flat or smooth shading</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glShadeModel</b>(</code></td><td>GLenum <var class="pdparam">mode</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">
                    <em class="parameter"><code>mode</code></em>
                </span></dt><dd><p>Specifies a symbolic value representing a shading
                    technique. Accepted values are <code class="constant">GL_FLAT</code> and
                    <code class="constant">GL_SMOOTH</code>. The initial value is
                    <code class="constant">GL_SMOOTH</code>.</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>GL primitives can have either flat or smooth shading.
        Smooth shading, the default, causes the computed colors of
        vertices to be interpolated as the primitive is rasterized,
        typically assigning different colors to each resulting pixel
        fragment. Flat shading selects the computed color of just one
        vertex and assigns it to all the pixel fragments generated by
        rasterizing a single primitive. In either case, the computed
        color of a vertex is the result of lighting if lighting is
        enabled, or it is the current color at the time the vertex was
        specified if lighting is disabled.</p><p>
            Flat and smooth shading are indistinguishable for points.
            Starting when <a class="citerefentry" href="glDrawArrays"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
            or <a class="citerefentry" href="glDrawElements"><span class="citerefentry"><span class="refentrytitle">glDrawElements</span></span></a>
            is issued and counting vertices and
            primitives from 1, the GL gives each flat-shaded line segment
            <math overflow="scroll"><mi mathvariant="italic">i</mi></math>
            the
            computed color of vertex
            <math overflow="scroll">

                <mrow>
                    <mi mathvariant="italic">i</mi>
                    <mo>+</mo>
                    <mn>1</mn>
                </mrow>
            </math>,
            its second vertex.
            Counting similarly from 1,
            the GL gives each flat-shaded polygon the computed color of the vertex listed
            in the following table.
            This is the last vertex to specify the polygon.
        </p><p>
        </p><div class="informaltable"><table><colgroup><col /><col /></colgroup><thead><tr><th><span class="bold"><strong>
                        Primitive Type of Polygon
                        <math overflow="scroll"><mi mathvariant="italic">i</mi></math>
                        </strong></span></th><th class="center"><span class="bold"><strong>
                        Vertex
                        </strong></span></th></tr></thead><tbody><tr><td>
                        Triangle strip
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mi mathvariant="italic">i</mi>
                                <mo>+</mo>
                                <mn>2</mn>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Triangle fan
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mi mathvariant="italic">i</mi>
                                <mo>+</mo>
                                <mn>2</mn>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Independent triangle
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mn>3</mn>
                                <mo>⁢</mo>
                                <mi mathvariant="italic">i</mi>
                            </mrow>
                        </math>
                        </td></tr></tbody></table></div><p>Flat and smooth shading are specified by
        <code class="function">glShadeModel</code> with
        <em class="parameter"><code>mode</code></em> set to
        <code class="constant">GL_FLAT</code> and
        <code class="constant">GL_SMOOTH</code>, respectively.</p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_ENUM</code> is generated if
        <em class="parameter"><code>mode</code></em> is any value other than
        <code class="constant">GL_FLAT</code> or <code class="constant">GL_SMOOTH</code>.</p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
        <a class="citerefentry" href="glColor"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a>,
        <a class="citerefentry" href="glColorPointer"><span class="citerefentry"><span class="refentrytitle">glColorPointer</span></span></a>,
        <a class="citerefentry" href="glLight"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,
        <a class="citerefentry" href="glLightModel"><span class="citerefentry"><span class="refentrytitle">glLightModel</span></span></a>,
        <a class="citerefentry" href="glMaterial"><span class="citerefentry"><span class="refentrytitle">glMaterial</span></span></a>
        </p></div><div class="refsect1" title="Copyright"><a id="copyright"></a><h2>Copyright</h2><p>
            Copyright © 2003-2004
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div>
